Simon, 59, has also made a promise to give away his entire Hollywood fortune -- valued at $100 million -- to charity. He reveals that animal welfare and feeding the homeless are causes that are especially important to him. His Sam Simon Foundation's "Feeding Families" program alone feeds 400 families a day in Los Angeles.

As for his contributions to animal welfare organizations, he says it's been a remarkably therapeutic experience.

"Ingrid Newkirk, who is the founder of PETA and is one of the most influential and important people in my life and on the planet, she came up with an almost therapy for me, where we planned -- and are still planning -- a series of animal liberations and actions that I get to participate in and enjoy and have something to look forward to at the same time we're helping some animals," he explains about his involvement with People for the Ethical Treatment of Animals (PETA), which sells the "Seaworld Kills" shirt he's wearing.

"I think that my passion for the animals ... is based on the knowledge that these creatures who feel, and think, can't speak for themselves," he adds. And they're dependent on us for that. And so I feel it's my responsibility to speak for those who can't speak for themselves."

Simon was originally just given three to six months to live when he was diagnosed with terminal colon cancer in 2012.

"They showed me my scans and said, 'These are the scans of a dead man,'" he said. "I said, 'Is it curable?' And the doctor goes, 'We don't use that word.'"

Though despite his disease, he surprisingly says he's "never been happier."

"I feel great," he says. "Somehow I ended up surrounded by people that love me and take care of me and would do anything for me. It's a good feeling. That's called happiness. I think I may have had a problem letting it in before."